Experimental Study on Concrete Using Copper Slag as Replacement Material of Fine Aggregate

This paper reports the effect of concrete using copper slag as fine aggregate replacement. In this project work, the concrete grade M40 was selected and IS method was used for mix design. The properties of material for cement, fine aggregate, coarse aggregate and copper slag were studied for mix design. The various strength of concrete like compressive, flexural and split tensile were studied and non-destructive test such as rebound hammer test and ultrasonic pulse velocity measurement were studied for various replacements of fine aggregate using copper slag that are 0%, 20%, 40%, 60%, 80% and 100%. The maximum compressive strength of concrete attained at 40% replacement of fine aggregate at 7 and 28 days. The split tensile strength and the flexural strength were also obtained higher strength at 40% replacement level at 28 days. The rebound hammer test showed higher compressive strength at 40% fine aggregate replacement, this is due to uniformity of concrete. The pulse wave velocity is higher for the 40% fine aggregate replacement, it is understood that the density of the mix is high and free from pores. *Corresponding author: Tamil Selvi P, Department of Civil Engineering, Dr. Sivanthi Aditanar College of Engineering, Tiruchendur-628215, Tamilnadu, India, Tel: +91-4639-242-482; E-mail: tamse10@gmail.com Received June 11, 2014; Accepted September 29, 2014; Published October 05, 2014 Citation: Tamil Selvi P, Lakshmi Narayani P, Ramya G (2014) Experimental Study on Concrete Using Copper Slag as Replacement Material of Fine Aggregate. J Civil Environ Eng 4: 156. doi:10.4172/2165-784X.1000156 Copyright: © 2014 Tamil Selvi P, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Introduction
Concrete is a composite material composed of water, coarse granular material (the fine and coarse aggregate or filler) embedded in a hard matrix of material (the cement or binder) that fills the space among the aggregate particles and glues them together. Concrete is widely used for making architectural structures, foundations, brick or block walls, pavements, bridges or overpasses, highways, runways, parking structures, dams, pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Concrete is used in large quantities almost everywhere mankind has a need for infrastructure [1].
The amount of concrete used worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined. Concrete's use in the modern world is exceeded only by that of naturally occurring water. Concrete is also the basis of a large commercial industry. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $100 billion in revenue by 2015. In the United States alone, concrete production is a $30-billion-per-year industry, considering only the value of the ready-mixed concrete sold each year. Given the size of the concrete industry, and the fundamental way concrete is used to shape the infrastructure of the modern world, it is difficult to overstate the role this material plays today [2,3].
Copper slag is used in the concrete as one of the alternative materials. It is the waste product of copper from Sterlite Industries India Ltd, Tuticorin. The safe disposal of this waste is a lack, costly and causes environmental pollution. The construction industry is the only area where the safe use of waste material (copper slag) is possible. When it is introduced in concrete as a replacement material, it reduces the environmental pollution, space problem and also reduces the cost of concrete.
However, further additions of copper slag caused reduction in the strength due to an increase of the free water content in the mix. Mixes with 80% and 100% copper slag replacement gave the lowest compressive strength value of approximately 80 MPa, which is almost 16% lower than the strength of the control mix. The results also demonstrated that the surface water absorption decreased as copper slag quantity increases up to 40% replacement; beyond that level of replacement, the absorption rate increases rapidly. Therefore, it is recommended that 40 wt% of copper slag can used as replacement of sand in order to obtain HPC with good strength and durability properties [4,5].

Materials
There are many types of concrete available, created by varying the proportions of the main ingredients below. In this way or by substitution for the cementitious and aggregate phases, the finished product can be tailored to its application with varying strength, density, or chemical and thermal resistance properties.
Aggregate: Aggregate consists of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestone, or granite, along with finer materials such as sand. The fine aggregate used in this study is river sand conforming to grading zone II Table 1 of IS 383 [6]. The coarse aggregate used in this study is of angular in shape and the maximum nominal size of coarse aggregate is 20 mm and it is Conforming to Table 2 of IS 383 [6].

Objective of this study
Many researchers had already found, copper slag possible to use as a material in concrete. In this experimental study copper slag is used in concrete as replacement material of fine aggregate. For this study, M40 grade of concrete is used and the tests are conducted for various replacement of fine aggregate using copper slag as 0%, 20%, 40%, 60%, 80% and 100% in concrete. The obtained results are compared with those of control concrete made with fine aggregate [10].

Properties of materials
The preliminary tests were carried out for finding the materials properties of cement, fine aggregate and coarse aggregate as per IS 12269 [7] and IS 383 [6]. The studied properties are given in Tables 1 and 2.

Methodology
In fresh state; the workability parameters such as slump value and compacting factor were studied. In hardened state; the strength tests such as compressive strength, split tensile strength and flexural strength were studied and the Non-destructive tests such as rebound hammer test and ultrasonic pulse velocity test were conducted for each mix. The obtained results are tabulated. The conclusions were made from the results and discussions (Table 3).

Mix design
An integral part of concrete mix proportioning is the preparation of trial mixes and effect adjustments to such trials to strike a balance between the requirements of placement, that is, workability and strength, concomitantly satisfying durability requirements 4 [11]. As per IS 10262 [12], the method is adopted for finding the proportion of M40 grade concrete and the arrived mix ratio was 1:1.36:2.52:0.41 (Tables 4 and 5).

Experimental work
Workability: Workability is a measure of the ease with which a fresh mix of concrete or mortar can be handled and placed. For various mixes the concrete were prepared. In the fresh concrete, the slump cone test and compaction factor test were carried out ( Figure 2). • Compacting factor test: Compacting factor of fresh concrete is done to determine the workability of fresh concrete by compacting factor test as per IS 1199 [13]. The apparatus used is Compacting factor apparatus ( Table 6).        [16]. The split tensile strength (N/mm 2 ) is calculated by using the formula, Non-destructive test: In the hardened concrete, the Nondestructive tests like Rebound hammer test & Ultrasonic pulse velocity test were carried out as per IS 13311 [17,18].

Rebound hammer test:
A Schmidt hammer, also known as a Swiss hammer or a rebound hammer, is a device to measure the elastic properties or strength of concrete or rock, mainly surface hardness and penetration resistance. The hammer measures the rebound of a spring-loaded mass impacting against the surface of the sample. By reference to the conversion chart, the rebound value can be used to determine the compressive strength.
Ultrasonic pulse velocity test: Ultrasonic Pulse Velocity (UPV) testing of concrete is based on the pulse velocity method to provide information on the uniformity of concrete, cavities, cracks and defects. The test equipment must provide a means of generating a pulse, transmitting this to the concrete, receiving and amplifying the     pulse and measuring and displaying the time taken (Figure 4, Tables  10 and 11).

Study on fresh concrete
Based on the observations from the experimental work, the following results and discussions are presented in this chapter. For workability study, the slump and compacting factor test were conducted on fresh concrete for different proportions as mentioned in Table 5.
Slump value: From Figure 5 it was noted that the slump value increased with the percentage of copper slag increases in concrete. The measured slump was 26 mm for the control mixture whereas 36 mm with 100% replacement of fine aggregate using copper slag. This considerable increase is due to the low water absorption characteristics of copper slag and its glassy surface compared with sand which caused surplus quantity of free water to remain after the absorption and hydration processes have completed. It should be noted that mixes with high contents of copper slag showed signs of bleeding and segregation which can have detrimental effects on concrete performance [19].
Compacting factor: From Figure 6 it was noted that the value of compacting factor slightly increased with the replacement of copper slag in concrete. The calculated value of compacting factor was 0.82 for the control mixture whereas 0.96 with the 100% replacement of copper slag. This is mainly due to the higher specific gravity of copper slag which was 3.45 compared with sand which has a specific gravity of 2.47.

Study on hardened concrete
In this section, based on the experimental results of the compressive strength, split tensile strength, flexural strength, rebound hammer test and ultrasonic pulse velocity measurement discussions are made as follows.
Compressive strength: From the Figure 7 it was found that the weight of the cube showed lowest value in control concrete at before curing, 7 days curing and 28 days curing were 8.037 kg, 8.309 kg and 8.494 kg respectively whereas in concrete with 100% fine aggregate replacement using copper slag, the weight of the concrete value found the highest at before curing, 7 days curing and 28 days curing were 9.631 kg, 9.725 kg and 9.918 kg. The weight of specimen increased with the addition of copper slag into concrete. This is because of higher density of copper slag which was 2197 Kg/m 3 compared with density of sand which was 1700.67 Kg/m 3 . Figure 8 showed that the compressive strength of cube was found to be 29.50 N/mm 2 at 0% fine aggregate replacement and of 38.88 N/mm 2 at 100% fine aggregate replacement of 7 days. And the compressive strength of cube at 28 days was found to be 26.87 N/mm 2 at 0% fine      aggregate replacement and of 27.66 N/mm 2 at 100% fine aggregate replacement. The maximum compressive strength was found to be at 40% fine aggregate replacement of about 38.37 N/mm 2 at 7 days and of 42.97 N/mm 2 at 28 days. The compressive strength of concrete at 7 and 28 days increased gradually up to 40% fine aggregate replacement and then decreased with increase in percentage of replacement.

Replacement of fine
Split tensile strength: Figure 9 showed that the split tensile strength of cylinder was found to be 2.45 N/mm 2 at 0% fine aggregate replacement and of 1.85 N/mm 2 at 100% fine aggregate replacement. The maximum split tensile strength was found to be at 40% fine aggregate replacement of about 3.09 N/mm 2 . The split tensile strength of copper slag added concrete was gradually increased up to 40% replacement and then decreased with further fine aggregate replacement. The split tensile strength of cylinder showed a similar behaviour to the compressive strength of the cube for all mixtures.
Flexural strength: Figure 10 showed that the flexural strength of beam was found to be 4.79 N/mm 2 at 0% fine aggregate replacement and of 4.42 N/mm 2 at 100% fine aggregate replacement. The maximum flexural strength of beam was found to be at 40% fine aggregate replacement of about 7.73 N/mm 2 . The flexural strength of beam showed higher strength at 40% fine aggregate replacement. The flexural strength of all mixtures showed a similar behaviour to the compressive strength results. Figure 11 it is noted that the compressive strength was found to be 9.81 N/mm 2 at 0% fine aggregate replacement and of 14.73 N/mm 2 at 100% fine aggregate replacement of 7 days. And the compressive strength at 28 days was found to be 10 N/ mm 2 at 0% fine aggregate replacement and of 20.08 N/mm 2 at 100% fine aggregate replacement. The maximum compressive strength was found to be at 40% fine aggregate replacement of about 26.49 N/mm 2 at 7 days and 35.64 N/mm 2 at 28 days. The compressive strength of concrete at 7 and 28 days obtained with the rebound number was increased gradually up to 40% fine aggregate replacement and then decreased with increase replacement. This is due to homogeneity of concrete and the strengths were lie in between ± 15% and ± 20% of compressive strength of compression test.

Rebound hammer test: From the
Ultrasonic pulse velocity measurement: The ultrasonic pulse velocity measurement is the measure of quality of concrete. It is mainly related to its density and modulus of elasticity which in turn, depends upon the materials and mix proportions used in making concrete as well as the method of placing, compaction and curing of concrete. From Figure 12 it was observed that the pulse wave velocity showed above 4.5 km/sec at 7 th day measurement and above 5.2 km/sec at 28 th day measurement. This is due to the density of the mix is high and free from pores. It is also observed that the concrete at 40% replacement level showed excellent quality and good quality for other percentages at 7 th day measurement [20]. At 28 th day measurement, the concrete showed excellent quality for 20%, 40%, 60% and 80% replacement of fine aggregate and showed good quality for 0% and 100% replacement of fine aggregate. The important observation was that the addition of copper slag definitely reduced the pores of concrete and made the concrete impermeable (Figure 13).

Conclusion
From the results and discussions, the following conclusions were made • The replacement of fine aggregate using copper slag in concrete increases the density of concrete thereby increases the selfweight of the concrete.
• The workability of concrete increased with the increase in copper slag content of fine aggregate replacements at same water-cement ratio.
• Form the results of compressive strength, split tensile strength and flexural strength, the concrete shown higher value at 40% replacement of fine aggregate using copper slag. So it is recommended that 40% of fine aggregate can be replaced by copper slag.
• The rebound hammer test revealed the uniformity of concrete and their compressive strength.
• The ultrasonic pulse velocity test indicated the excellent quality of concrete at 40% replacement level.
• The construction industry is the only area for safe use of waste materials, which reduces the environmental problems, space problems and cost of construction.